That is true. But for WiFi chips, some of that initial development cost can be bypassed as they usually operate over a SDIO interface, which is a generic interface and compatible with most microcontrollers with a SDIO controller.

So you can usually just get the WiFi chip (for example, Broadcom or Marvell) on a SDCard form-factor extender, plug it into your standard SD Card slot and work on it with the SDIO controller on your development board.

Note: the SD interface controller must support SDIO and not just the memory SD-Card portion of the spec.

But, of course, you still need the development documentation and internal chip information. That, unfortunately, must still be paid for.